1. Field of the Invention
The invention relates to a microinjector head and its manufacturing method, and more particularly, to a microinjector head with a driving circuitry and the manufacturing method of the microinjector head.
2. Description of the Prior Art
At present, droplet injectors are widely applied in inkjet printers. Droplet injectors also have many other applications in different fields such as fuel injection systems, cell sorting, drug delivery systems, direct print lithography and micro jet propulsion systems. The common aim of the above applications is to provide a droplet injector that is reliable, of low-cost, and provides high-quality droplets with a high frequency and a high spatial resolution.
However not all apparatuses can successfully inject uniform droplets. In currently known and used droplet injection systems, one system using thermally driven bubbles to inject droplets is proved to be a successful system because of its comparatively simple architecture and lower cost.
U.S. Pat. No. 6,102,530-xe2x80x9cApparatus and method for using bubbles as virtual valve in microinjector to eject fluidxe2x80x9d mentions a droplet injection apparatus with virtual valves as shown in FIG. 1. Heaters 20, 22 are located around orifices 18. A first bubble is generated between a manifold 16 and a fluid chamber 14. Therefore the first bubble acts like a virtual valve and is capable of reducing a cross talk effect with the adjacent chambers. A second bubble is then generated and approaches the first bubble to push the fluid, causing a droplet to be ejected from the orifice 18. Finally, the second bubble fuses with the first bubble and successfully reduces the production of satellite droplets.
U.S. Pat. No. 5,122,812-xe2x80x9cThermal inkjet print head having driver circuitry thereon and method for making the samexe2x80x9d mentions a structure of an inkjet print head with driving circuitry as shown in FIG. 2. Heating devices and driving circuitry are integrated on a same substrate. However there are still many steps in the process. And according to the structure, a barrier layer 130 of 20xcx9c30 xcexcm in thickness must be formed and an orifice plate is adhered on the barrier layer 130. This adhesion procedure limits the spatial resolution due to unavoidable assembly tolerance. In addition, the adhesion procedure is not compatible with general IC processes. When microinjector arrays are integrated with driving circuitry to reduce layout and are tightly packed, such incompatibility problems become more obvious and lead to more complicated manufacturing processes and thus higher costs.
It is therefore a primary objective of the claimed invention to provide a microinjector head with driving circuitry to control a plurality of first and second bubble-generating devices to eject fluid in a plurality of chambers from orifices. A secondary objective of the claimed invention is to provide a manufacturing method for making a microinjector head with driving circuitry in fewer steps and with fewer number of circuit devices and linking circuits.
According to the claimed invention, the microinjector head with driving circuitry to eject fluid uses a bubble as a virtual valve. The microinjector head comprises a plurality of chambers, a manifold connected to the chambers for providing fluid to the chambers, a plurality of orifices open to corresponding chambers, a plurality of pairs of bubble generators, each pair of bubble generators comprising a first and a second bubble-generating devices near a corresponding orifice and above the corresponding chamber, the first bubble-generating device generating a first bubble that is used as a virtual valve, the second bubble-generating device generating a second bubble to cause liquid in the chamber to eject from the orifice when the chamber is filled with fluid, and a driving circuit comprising a plurality of functional devices disposed on a same substrate. The driving circuit can send a driving signal to a specific pair of bubble generators so as to eject droplets out of the corresponding orifices. The first bubble generator and the second bubble generator may be two resistive heaters with different resistances and may be connected to each other in series.
It is an advantage of the claimed invention that the microinjector head and the manufacturing method provide a micro droplet injector head manufactured with lower cost and fewer procedures.
These and other objects and the advantages of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.